Microscope slides can be made by joining a flat, transparent slide plate and a thin flat transparent cover slip over the specimen. Commercially made microscope slides, such as the one disclosed herein in detail, can be made by joining round pegs in mating round bases. The interference fit formed creates a unitary slide--cover slip that can be used for clinical testing.
One purpose for which a specimen so prepared is examined is to permit quantitative microscopic analysis of particulate matter in the fluid. Fluids which are typically examined by such procedures include urine, blood, spinal fluid, sputum and cell cultures. When the specimen has been spread to a film of generally uniform thickness, the technician is able to count the number of solid particles, cells and the like in a given area of the specimen and this count is indicative of the content of the specimen per unit volume thereof. The actual volume of fluid confined beneath a given area of the cover slip is dependent upon several variables, among them being the size of the drop of liquid applied to the slide plate, the viscosity of the fluid, the force applied in squeezing the glass cover slip against the plate and the flatness of the two elements in their confronting relationship. The distribution of solid particles in the specimen, particularly larger particles, can be affected by the squeezing action, and slippage can occur between the cover slip and the plate, thereby possibly adversely affecting the accuracy of the examination. Because the thickness of sample depends on the amount of sample placed on the slide, as much as a 50-200 percent error can be introduced.
Such microscope slides are usually made from molded glass. Plastic slides and cover slips, such as disclosed in U.S. Pat. No. 4,607,921 to Miller solve many of the problems associated with glass slides and cover slips. But, the plastic slide or cover slip can tend to warp slightly during the molding process. A warped slide will not mate properly with a warped coverslip. The resultant assembly will be itself warped. If the slide and coverslip are warped strongly enough one will not be able to join its partner.
Plastic slide warpage can be cured by a separate step wherein the finished slide is heated and pressed. But this adds another step in producing what is intended to be an inexpensive disposable item. Furthermore, if the warpage is so bad the parts can mate, then even this added step cannot cure the problem.
It would be advantageous to have a method of joining molded plastic pieces that allowed easy fit in slightly warped pieces. Especially preferable would be a method that corrected any warpage automatically.